e. Write recursive predicates to solve problems: Calculating factorial, and Finding the nth Fibonacci number

 

factorial(0,1).

factorial(N,Ans):-

       N>0,

       N1 is N-1,

       factorial(N1,Ans1),

       Ans is N*Ans1.

fib(0,0).

fib(1,1).

fib(N,Ans):-

    N>1,

    N1 is N-1,

    N2 is N-2,

    fib(N1,Ans1),

    fib(N2,Ans2),

    Ans is Ans1+Ans2.

go:-

     factorial(5,Ans),

     write(Ans),nl,

     fib(3,Ans3),

     write("3rd fibonacci : "),nl,

     write(Ans3).